Handling of the blood outside the body, referred to as extracorporeal, is frequently used in medical procedures in treatments such as blood-oxygenation, plasmapheresis, leukopheresis, hemopheresis, extracorporeal chemotherapy, hyperthermia, hypothermia, bone marrow transfusions, blood transfusions processing by heart lung machines during surgery and dialysis for patients with kidney failure. In such procedures there is always a risk that homolysis, or the breaking of red blood cells, may occur.
As is known to those practicing the art, the breaking of blood cells is deleterious not only from the loss of the function of those cells, but also by the release into the blood plasma of hemoglobin which is toxic.
Heretofore, in hemodialysis, hemoperfusion, blood transfusion and other extracorporeal blood therapies, whether hemolysis occurred was determined by taking blood samples and subjecting them to analysis. This is typically done by taking the sample to a laboratory to separate red blood cells from plasma and looking for the artifacts of hemolysis, such as hemoglobin, in the plasma.
This approach is not usually satisfactory because of the damage that can be done to a patients blood while the test is being performed. It is also possible that hemolysis may occur to a significant degree between the time in which the tests are performed.
Currently there is no system available for on-line hemolysis detection. It is, therefore, impossible to have continuous, on-line detection of hemolysis in a red blood containing components such as packed blood cells, buffy coat or whole blood in a blood line. Hemolyzed blood is dangerous to the patient due not only loss of blood cells, but more importantly the toxic effects of free hemoglobin.
Detection of hemolysis in plasma is further complicated by the fact that the characteristics of plasma, in particular color, vary from individual to individual and varies for a single individual over time depending of such factors as diet, and other metabolic differences that manifest themselves in the blood.
While the prior art has concerned itself with methods and apparatus for separation of blood components, these have not been employed to detect hemolysis on a real-time, continuous basis.
For example, U.S. Pat. No. 3,705,100 to Blatt et al. describes a method and apparatus for fractionating blood in order to separate the blood components that may be desirable in blood transfusions. Taught is the use of centrifugal separation techniques and the use of a filtration membrane such as anisotropic and depth filter membranes. This allows the plasma component of blood to be used in an emergency while the formed elements of the blood such as red blood cells, white blood cells, and platelet are returned to the donor so that more frequent bleedings can be taken.
U.S. Pat. No. 4,191,182 to Popovich, et al. describes a method and apparatus for plasmapheresis. Again, the system described employs a membrane with the appropriate pore sized to fractionate blood into cellular and plasma components. This reference particularly points out that flow rates are important to attaining the desired result using the specified sheer stresses and pressures on the membrane ultra filter.
U.S. Pat. No. 4,350,156 to Malchesky, et al. describes a continuous, on-line system and apparatus for removing macromolecules from a physiological fluid such as blood. Membranes are employed in a blood flow path to separate blood plasma, cellular components, and macromolecules that are associated with progress of a variety of diseases. Removal of these molecules inhibits the progress of certain diseases.
U.S. Pat. No. 4,374,731 to Brown, et al. describes a method and apparatus for performing plasmaphereses while controlling the plasma collection rate through a plasmapheresis membrane filter. By regulating the pressure on the plasmapheresis membrane filter, the flow of plasma therebetween can be controlled.
The goal of these prior art patents is to separate as much plasma as possible from the blood for therapeutic or collection purposes. Therefore, these membranes plasmapheresis devices normally have a membrane surface area in the range of several thousand square centimeters in a plasma port in the plasma compartment through which the plasma can be collected for removal or further treatment before it is returned back to the patient.
It is an object of the present invention to provide an on-line device that can continuously detect hemolysis that may be developing in a blood path. It is a further object that such device be capable of performing without attention or replacement.
It is another object of the invention to provide a device that does not require careful manual calibration, adjustment or interpretation to distinguish between variabilities in normal blood plasma among people or between an individual's blood at different times.
Another object of the present invention is to provide a device that is simple and sufficiently inexpensive that the portion of the device in contact with the patient's blood is disposable so that contamination between patients is eliminated.